Aeronautical propeller



s. REED AERONAUTICAL PROPELLER April 26, 1932.

Filed Aug. 6, 1929 vllllllli INVENTOR Patented A rxzs, 1932 UNITED.STATES PATENT OFFICE SYLVANUS A. REED, OF NEW YORK, N. Y., ASSIGNOR TOREED PBOPELLER CO. INC., OI

GARDEN CITY, NEW YORK, A CORPORATION OF NEW YOB? AERONAUTICAL PROPELLERApplication filed August 6, 1929. Serial No. 388,921.

My invention relates. to aeronautical propellers.

In a previously filed application, Serial #348,587, now Patent 1,778,340issued Oct.

14, 1930, solid metal propeller blades having in one or both facesthereof weight reducing recesses not injuriously "impairing the requiredstructural strength of the blades are described and illustrated. Wheresuch recesses are provided it is proposed to use nonstructural surfacerestoring means or devices. In Fig. 3 of said patent there isillustrated a form of propeller having separate and detachable blades,which said blades at their inner ends, are preferably substantiallycylindrical and anchored, in any suitable manner, to and within the sidebranch ferrules of a propeller hub. Such a propeller is also illustratedin the drawings of the present application.

As distinguished from said earlier filed application, the presentinvention contemplates improved means whereby this latter type or formofpropeller blade may be reduced, orfurther reduced in weight, whichmeans consists in boring a hole into the inner cylindrical end of theblade, leaving thereby a substantially cylindrical shell with wallssufficient in strength and thickness to sustain safely the operativestresses of the propeller. Preferably said hole is extended into theblade a certain distance, and beyond its termination, if desired, theweight reducing depressions or recesses and surface restoring meansabove referred to, may be provided. Where a heavy material such as steelis utilized for propeller blades, such or any weight reductionconsistent with retaining in the blade sufiicient strength is of theutmost importance.

In the drawings, wherein like reference characters denote like orcorresponding parts, Fig. 1 is a plan View of a detachable blade metalaeronautical propeller embodying my invention, the propeller bladeshaving formed therein lightening recesses, and the recesses of one bladebeing shown uncovered;

Fig. 2 is an enlarged view, somewhat similar to Fig. 1, showing indotted lines the line 3-3 of In the embodiment of the invention selectedfor illustration, 'separate and detachable blades 1010 are shown asanchored at their inner ends in the side branch ferrules 1111 of a metalhub 12. Said blades 1010 are preferably solid throughout and each in itsentirety is'forged hot between steel dies, preferably from alloy steel,having high tensile strength, elasticity and fatigue limit, but may, ifdesired, be made of other forged or rolled metal alloys such, forinstance, as strong alloys of aluminum or magnesium. The desired pitchangle of the blades may be obtained in any Well known manner. Preferablysaid-blades, at their inner ends, are. anchoredwithinthe ferrules 11 asby interlocking shoulders and recesses 1314 as shown (see Fig. 4), or,if desired, the anchorages may be so formed and constructed as to admitof blade adjustment both axially and rotatably. Such anchorage and/oradjustments, however, form no part of the present inventlon.

Within the inner end of the stem portion of each blade 10, a hole'15 isbored longitudinally of the blade axis, which said hole, throughoutaportion of its depth, may be reduced in diameter as indicated at 16. Theblades 10, at their inner ends, being substantially cylindrical incross-section, the holes 1516 are preferably similarly formed and ofsuch size and depth as toprovide for a maximum of weight reductionconsistent with leaving in the walls of the blade stems or inner endportions that strength and bulk of material necessary to sustain safelythe stresses of service operation. Or, if desired, the holes 15-16 maybe extended for a certain distance along the axes of the blades, andbeyond the termination of the holes, the

weight reducing depressions or recesses 17 disclosed in my said earlierfiled application, may be utilized. Whether the holes 15-16 are usedalone or in combination with the lightening recesses, an exceptionallylight though strong solid metal propeller blade is obtained.

The most eflicient diameter and length for the bores vary with differentmetals and different grades of the same metal. when my invention isapplied to a propeller, preferably (as shown in Figs. 2 and 4) thediameter of the larger bore approximates of the diameter of thecylindrical inner end portion and the outer end of the longer boreextends to a point approximating l/Gth of the blade length from the axisof the propeller, but I do not confine myself to any given size or depthof hole, nor to any special means of restoring the blade surfaces wherelightening depressions or recesses are provided. In boring the holesinto the blade stems, from the inner blade ends along the longitudinalaxes of the blades, only that portion of each'blade having an excess ofbulk and material is affected. N o deviation from the conventionalexterior shape and size of the inner blade ends is required and itbecomes unnecessary moreover, to provide a propeller hub of a differentform than that now extensively used.

While I have described my invention in detail in its present preferredembodiment, it will be obvious to those skilled in the art afterunderstanding my invention, that various changes and modifications maybe made therein without departing from the spirit or scope thereof. Iaim in the appended claims to cover all such modifications and changes.

What I claim is:

1 A propeller blade having a substantially cylindrical inner end portionadapted for anchorage to a propeller hub, said blade havingformed withinsaid inner end portion a longitudinally extending bore of such width anddepth as to provide for maximum weight reduction consistent withretaining in the wall of the bore sufficient strength to sustain safelythe stresses of service operation. I

2 A propeller blade having a substantially cylindrical inner end portionadapted for anchorage to a propeller hub, said blade havingitscylindrical inner end portion bored substantially along the longitudinalblade axis and said bore having a maximum of width and depth consistentwith retaining in 1ts defining wall sufiicient strength and bulk ofmaterial to sustain safely the stresses of service-operation.

3. propeller blade having a substantially cylindrical inner end portionadapted for anchorage within a side branch ferrule of a.

propeller hub, said blade having its cylindrical inner end boredsubstantially along the longitudinal blade axis, and said bore extend-1ng radially out from said inner blade end and However,

having a maximum of width and depth consistent with retaining in theinner end portion of the blade sufficient bulk and strength of materialto sustain safely the stresses of service operation.

4. A propeller blade having a substantially cylindrical inner endportion adapted for anchorage to a propeller hub, said blade havingformed within said inner end portion a longitudinaly extending bore ofsuch width and depth as to provide for maximum -weight the innertwo-thirds of the blade length, sur- 7 face recesses for further weightreduction, and non-structural surface restoring means associated withsaid recesses.

(3. In an aeronautical propeller, an integral blade having asubstantially cylindrical inner portion and having formed within saidinner portion a weight reducing ldngitudinally extending bore, said borebeing confined to the inner two-thirds of the blade length.

7. In an aeronautical propeller, a propeller hub, an integral and solidblade having a substantially cylindrical inner end portion adapted foranchorage to said propeller hub, said blade having forined within saidinner end portion a longitudinally extending bore and having formedbeyond said first named bore a second longitudinally extending bore ofsubstantially smaller diameter than the first mentioned bore.

8. In\ an aeronautical propeller, an integral and solid blade having asubstantially cylindrical inner end portion and having formed withinsaid inner end portion a longitudinally extending bore, the diameter ofsaid bore being less than 80% and more than 50% of the .diameter of saidcylindrical inner end portion.

9. In an aeronautical propeller, an integral and solid blade having asubstantially cylindrical inner end portion and having formed withinsaid inner end portion a lo-gitudinally extending. bore, the diameter ofsaid bore being less than 80%,of the diameter of said cylindrical innerend portion.

10. In an aeronautical propeller, an integral and solid blade having asubstantially cylindrical inner end portion and having formed wlthlnsaid inner end portion a lonmesses gitu'dinally extending bore, thediameter oi said bore being approximately of the diameter of thecylindrical inner end portion.

11. 'A propeller blade having a substantially cylindrical inner endportion adapted for anchorage Within a side branch ferrule of apropeller hub, said blade having a longitudinally extending borebeginning at its inner end and terminating at a point within saidferrule, whereby the weight of the blade is lessened without affectingits strength.

12. A ropeller blade having a substantially cylindrical inner endportion adapted for anchorage within a side branch ferrule of apropeller hub, said blade having a longitudinally extending borebeginning at its inner end and termlnating at a point within saidferrule, a second bore extending longitudinally from the outer end ofsaid first named bore and of less diameter than the first named bore,whereby the weight of the blade is lessened without afi'ecting itsstrength.

In testimony whereof I hereunto afix my signature.

SYLVANUS A. REED.

